166 W. Crookes on the Wax-paper Photographic Process. 



kinds, and in every degree of purity : also to Mr. Maskelyne, 

 for a valuable series of the chemical bodies of which the various 

 waxes are composed ; by means of these, I have been enabled 

 to examine the effect produced by saturating the paper with 

 bees wax from different countries, Myrica wax, Canauba wax, 

 China wax, spermaceti, ethal, stearic acid, stearin, palmitic acid, 

 palmitin, paraffin, and various oils. 



22. I find that the action of the wax is purely mechanical, 

 almost the only difference of effect produced by any of the above 

 bodies, widely as they vary in their chemical nature, arising from 

 a difference in their physical properties. 



Stearin, palmitin, and most of the oils, are too greasy in their 

 nature to be advantageously employed. The fatty acids do not 

 make the paper in the least greasy, but they injure the transpa- 

 rency. China wax has almost too high a melting point, and 

 gives a crystalline structure to the paper. Spermaceti also is too 

 crystalline. Paraffin, ethal, and the waxes, produce very good 

 results; of these bees wax is the only one that would be prac- 

 tically available for this purpose. It should be free from stearin, 

 stearic acid, tallow, &o. ; the presence of a little spermaceti 

 does not much interfere, but as its price differs little from that 

 of pure wax, it is not so common an adulteration as the other 

 cheaper substances. 



23. It will be unsafe to use the wax in the form of round thin 

 tablets, about 4 inches in diameter, in which it is usually met 

 with, as in this state it is generally adulterated to the extent of 

 at least 50 per cent. 



As an article of commerce, it is next to impossible to obtain 

 small quantities of wax sufficiently pure to be relied upon. 

 The only way I can recommend is to apply to one of the well 

 known large bleachers, and trust to them for supplying the arti- 

 cle in a state of purity. Whenever I have found it necessary 

 to make such applications, my request has always been acceded 

 to in the most cordial manner, and every information has been 

 given with the utmost readiness. 



24. The other chemicals, (with the exception of the strong 

 nitric acid, which any retail druggist will supply, and the water, 

 which had best be distilled on the premises,) should be ordered 

 direct from some manufacturing chemist, as otherwise, unless the 

 operator have a sufficient knowledge of chemistry to be able to 

 detect any inferiority, there is danger of not having the articles 

 sufficiently pure. 



The iodid and bromid of potassium should be ordered purified. 



The nitrate of silver should be crystallized, not in sticks; it 

 ought to be perfectly dry, and have no smell, acid or otherwise. 



There are usually two varieties of glacial acetic acid to be met 

 with ; the purest must be used ; it should be perfectly free from 



